Surgical Knife Guide
ArthroLense | 2023
Objective: Develop a mechanical device that cooperates with ArthroLense’s AR technology to guide an orthopedic surgeon’s knife while cutting through bone. The mechanism must transverse in depth and rotate in pitch and yaw with all three of these motions being independent of each other. Additionally, the mechanism must be rigid so that its position is not altered by any forces exerted on it during the cut. Lastly, the guide should require minimal effort and only one hand to alter its position in any of these 3 DOFs, so that a surgeon can easily adjust it with one hand during surgery.
Conceptual Design
The process for this design began with substantial brainstorming sessions and various 2D sketches. Knowing that rotational DOFs were required, gears immediately came to mind and most of the design concepts revolved around this mechanism (pun intended). Worm gears were a noteworthy mechanism due to their single-input bidirectional abilities. Similarly, lead screws were another appealing mechanism due to their single-input rotational to translational abilities. As such, these two mechanisms were incorporated into the original sketches to facilitate the rotational and translational movements accordingly.
CAD
Following the conceptual design stage, the above 2D sketch was mocked up in SolidWorks. A total of 14 custom parts were designed and amassed into an assembly with pre-manufactured fasteners and bearings to create a realistic model of the design.
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The required motions are facilitated as follows:
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Depth- Lead screw located towards the rear of the image, connecting the gray and orange parts.
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Pitch- Worm gear housed in the yellow part rotates the entire center contraption (including the worm gear on the opposite side). Both light purple parts are joined to the dark purple parts with bearings to allow for this rotational motion.
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Yaw- Worm gear house din the light purple part rotates the center gear. The center of rotation is maintained at the center of the main gear through the use of second gear on the opposite side.
